Steroidogenic capacity of the placenta as a supplemental source of progesterone during pregnancy in domestic cats

Abstract

BackgroundUntil recently, the corpus luteum (CL) was considered to be the main source of progesterone (P4) during pregnancy in the domestic cat (Felis catus). However, other possible sources of P4 have not been ruled out. Although feline placental homogenates were found to be capable of synthesizing P4, expression of the respective steroidogenic enzymes has not been investigated at the molecular level. Therefore, in the present study, expression of the two major factors involved in the synthesis of P4 - 3beta-hydroxysteroid dehydrogenase (3betaHSD) and steroidogenic acute regulatory protein (StAR) - was investigated in the feline CL and placenta during the course of pseudopregnancy and pregnancy.MethodsThe mRNA levels of StAR and 3betaHSD were determined using Real Time PCR and their localizations were determined by immunohistochemistry. Placental P4 concentrations, after ethyl extraction, were measured by EIA.ResultsLuteal 3betaHSD and StAR mRNA levels were strongly time-dependent, peaking during mid-pregnancy. The placental 3betaHSD mRNA level was significantly upregulated towards the end of pregnancy. In the CL, 3betaHSD and StAR protein were localized in the luteal cells whereas in the placenta they were localized to the maternal decidual cells. Placental P4 concentrations were low in early pregnant queens, but increased along with gestational age.ConclusionsThese results confirm that the placenta is an additional source of P4 in pregnant queens and can thereby be considered as an important endocrine organ supporting feline pregnancy.

Ultrasonographic and progesterone changes during Days 21 to 63 of pregnancy in queens

“…Recent studies confirm that in pregnant queens, the placenta is an additional source of P 4 . Therefore, it should be considered as an important endocrine organ supporting feline pregnancy [7].…”

Synthesis and reception of prostaglandins in corpora lutea of domestic cat and lynx

“…After each qPCR reaction, melting curves were obtained by stepwise increases in temperature from 60 to 95°C to ensure single product amplification. Cyclophilin A was previously validated and selected among several different genes as a reference gene (Siemieniuch et al 2012. Quantification of qPCR results was performed by normalising the signals of target genes with the CYC signal using the real-time PCR Miner method, whereby calculation of reaction efficiency and the fractional cycle number at threshold (CT) were based on kinetics of individual qPCR reactions (Zhao & Fernald 2005).…”

“…This, however, does not rule out an intraluteal source of PGF 2α . In cats and lynxes, the prepartal PGFM elevation is accompanied by a decline in plasma P4 (Siemieniuch et al 2012, Painer et al 2014b, indicative of functional luteal regression; however, no complete structural regression, as suggested for the cat (Dawson 1946, Amelkina et al 2015a, is observed in lynxes (Painer et al 2014b). A smaller increase in plasma PGFM, concomitant with a P4 decrease, was shown in prooestrous lynxes (Painer et al 2014b).…”

“…(Paape et al 1975, Verhage et al 1976. The ongoing loss of steroidogenic capacity (Siemieniuch et al 2012, Zschockelt et al 2014 and the concomitant structural luteal regression (Dawson 1946, Amelkina et al 2015a) proceed similarly throughout the sequential luteal stages of pregnant and non-pregnant luteal phases. However, it is assumed that the respective corpora lutea (CL) enter the process of luteal regression at different time points, as CL of pregnant cats show early histomorphological signs of regression from days 38-39 onwards (Amelkina et al 2015a), whereas plasma P4 levels indicate that CL of non-pregnant cats begin to regress on day 21 after their formation (Paape et al 1975).…”

“…Information on cat-specific sequences for PTGS2/COX2 (GenBank accession EF036473 (Siemieniuch et al 2011)), PTGES (GenBank accession GU059259 (Siemieniuch et al 2013)), PGFS/AKR1C3 (GenBank accession HM490147 (Siemieniuch et al 2013)) and the validated reference gene cyclophilin A (CYC, GenBank accession AY029366 (Siemieniuch et al 2012) was published previously. Based on templates of feline luteal tissue, sequence information for PTGER2 (GenBank accession EF177829), PTGER4 (GenBank accession EF177830) and PTGFR (GenBank accession AF272340) was obtained for this study (Table 2).…”